Castle Island Weather Forecast

    • 50
    • 62

    Increasing Clouds

    • 51
    • 60

    Increasing Clouds

    • 50
    • 61

    Slight Chance Rain

    • 52
    • 62

    Partly Sunny

    • 52
    • 64

    Partly Sunny

    • 52
    • 63

    Partly Sunny

    • 52
    • 65

    Partly Sunny

Today 3 Sep San Juan County

Mostly sunny. A slight chance of Showers in the morning. Highs in the 60s. Southeast wind 10 to 20 Mph.

Tonight 3 Sep San Juan County

Partly cloudy. Lows in the upper 40s to mid 50s. Light wind.

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  • Temperature Real-Time

Castle Island Temperature Statistics

September Temperature

Whidbey Island Naval Air Station - Ault Field (8.1 miles)

  • Lowest 1 September, 2026

    51.1 °F

  • Average September

    58.3 °F

  • Highest 1 September, 2026

    64 °F

Climate (2021–2026)

Whidbey Island Naval Air Station - Ault Field (8.1 miles)

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  • Average Low 2021–2026

    44.4 °F

  • Average 2021–2026

    50 °F

  • Average High 2021–2026

    56 °F
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